This invention broadly relates to pumping apparatus and is specifically directed to sump draining apparatus capable of removing hazardous or toxic liquid from spill areas, landfills, leachate sumps, recovery wells and the like.
The presence of toxic and hazardous waste material represents a problem of increasing concern, particularly where such material is found beneath the surface of the ground. The presence of toxic and hazardous liquids in subsurface environments is particularly acute because of the possibility of leaching into water supplies and causing irreparable harm to natural environments.
In some cases, toxic and hazardous liquid waste is created by a particular environment and simply must be controlled by ongoing removal. In others, the liquid waste material finds its way into an environment in which it should not exist, and it must be removed to prevent the problem from spreading as well as to return the environment to its normal state.
An example of the first type of problem is the conventional landfill. Landfills that comply with environmental protection and pollution control regulations consist of a large ground recess the bottom and sides of which are lined with a liquid impermeable material to contain the waste as it is dumped into the recess. An ongoing problem, however, it the seepage of liquid to the bottom of the landfill, which may be waste material in liquid form or simply rain water that seeps through waste in more solid form. If the impermeable liner is punctured or ruptures, the liquid waste flows away from the landfill and creates a toxic or otherwise hazardous environment.
An example of the second type of problem mentioned above is the hydrocarbon spill from gasoline holding tanks at filling stations. These holding tanks are typically installed below the ground, and leaks developed in the tank or in the tank fittings create problems that are not only of a toxic nature but extremely hazardous as well. While it was once believed that such problems exist only in a small percentage of gasoline holding tanks, it is now being found that such problems are relatively commonplace.
Conventional sump draining devices are capable of efficiently removing some types of liquid in certain environments. However, some hazardous and toxic liquids and certain environments cause conventional sump draining apparatus to operate in a less than satisfactory manner.
As an example, conventional devices capable of efficiently removing liquid from larger sump sites are themselves relatively large, particularly in transverse dimension. While size is not necessarily a problem in a purely liquid environment, it becomes a significant problem for environments such as landfills, which include a significant amount of solid waste. It maybe necessary to install the sump draining apparatus to depths of up to 100 feet to remove the drained liquid, and installing such a device after the landfill is full or partially full is extremely difficult when larger pumping devices are used.
The relatively large size of conventional sump draining apparatus also makes them relatively expensive, particularly where multiple devices are necessary for large sump pits such as landfills.
Another problem with conventional sump draining devices is that they are typically designed to pump water, but not corrosive liquids or liquids which are flammable (e.g., gasoline). In a highly corrosive environment, conventional devices may lose efficiency relatively quickly, followed by a total breakdown. This problem is compounded when the pumping device is located at significant depths and cannot be easily replaced or repaired.
It is possible to overcome the corrosion problem with a stainless steel pump. However, pumps of this type have not been effectively incorporated into sump draining apparatus for use in environments such as landfills and other leachate sumps. Further, some conventional stainless steel pumps have pump inlets that are located at a point remote from the bottom of the pump, which structurally prevents the pump from being positioned at the extreme bottom of the sump pit as is necessary to remove substantially all the liquid.
A different problem is encountered in landfills that utilize a side slope riser conduit for the removal of hazardous and/or toxic liquid from a landfill. The side slope riser conduit typically consists of a length of pipe ranging from six inches to two feet in diameter, and which extends from a point outside the landfill along its sloping side surface to the extreme bottom of the landfill. The side slope riser conduit is closed at its extreme lower end, but perforated to permit the flow of leachate into the conduit at the lower end. A sump draining apparatus is installed in the conduit at its extreme lower end and is positioned to pump the liquid entering the lower end through an exhaust line projecting through the conduit to its upper end.
Conventional sump draining apparatus present a number of difficulties in the side slope riser conduit application, not the least of which is installing the apparatus. The conventional approach has been to place the sump draining apparatus on a type of skid that slides by gravity along the slope of the riser conduit, which typically has a slope of 3/1. To operate properly, the sump draining apparatus must be positioned at the extreme bottom end of the riser conduit, or it will not be in a position to be submerged into the leachate. Several problems have been encountered in such installations.
First, the sump draining apparatus must of necessity include an exhaust line connected to its outlet, which must be flexible to follow any bends in the riser conduit. Because the slope of the riser conduit is not extreme, the sump draining apparatus must be force fed along the conduit to its bottom. However, the flexibility of the outlet line does not permit it to be used to push the sump draining apparatus into place, and the deeper the sump draining apparatus travels into the riser conduit, the more difficult it is to force it farther. Skids have been employed in an effort to slide the sump draining apparatus to the bottom of the riser conduit, but with limited success. The slope of the riser conduit is often so shallow that friction between the skid and conduit causes the apparatus to come to a stop far short of the extreme lower end of the conduit. Further, skids increase the effective cross-sectional size of the sump draining apparatus, which makes movement of the apparatus difficult if not impossible when it encounters more than a gentle bend in the conduit.
Further, side slope riser conduits typically consist of a long straight section following the slope of the landfill side and terminating in a relatively short horizontal section that disposed at an angle relative to the longer section. The joint between the longer and short horizontal sections may create an angular bend that the sump draining apparatus cannot negotiate as discussed above. In addition, however, the two sections are conventionally joined with a thermal weld, which may include an internal bead that the skid cannot pass over.
All of the foregoing problems can prevent the sump draining apparatus from reaching its destination at the extreme lower end of the conduit if the apparatus is improperly positioned and it cannot operate properly. The problem is compounded by the fact that, without the utilization of expensive sensors, it cannot be determined when the sump draining apparatus reaches its destination.
Yet another problem encountered in the side slope riser conduit installation is misorientation of the sump draining apparatus when it reaches its destination. Preferably, the sump draining apparatus includes sensors used as limit controls to automatically start the sump pump in the presence of liquid, and to turn the pump off when the liquid level has diminished. These limit control sensors are sometimes mounted on the side of the sump draining apparatus, necessitating a specific orientation of the apparatus in order for them to operate properly. If misoriented, the automatic on-off control does not work properly.